The palaeontologists behind the discovery of Dreadnoughtus estimate it measured 26 metres from head to tail and weighed approximately 60 metric tonnes.

That is more than twice as long as a typical bus, and heavier than a Boeing 737.

The dinosaur weighed more than an adult sperm whale or a herd of African elephants - and seven times as much as the Tyrannosaurus rex.

Palaeontologist Kenneth Lacovara of Drexel University in the United States, who discovered the dinosaur and led its excavation, says its weight was calculated on the basis of the bones in its upper arm and thigh.

The scientists say the long-necked, long-tailed herbivore roamed the Earth about 77 million years ago.

They found a remarkably complete and well-preserved fossil in the southern Patagonia region of Argentina.

The dinosaur's neck measured 11.3 metres and its tail 8.7 metres.

Is this really the world's biggest dinosaur?

There's some dispute about this.

Professor Lacovara and his team say Dreadnoughtus was "substantially more massive than any other supermassive dinosaur for which mass can be accurately calculated".

Palaeontologists can only use the fossils they have found to estimate a dinosaur's weight.

In the case of Dreadnoughtus, the scientists have found a remarkably high 70 per cent of the skeleton's bones, not including the skull.

Another giant dinosaur, Argentinosaurus, may have been larger, Professor Lacovara says, but its scant remains do not allow a reliable weight estimate.

Only 13 bones out of approximately 250 in the Argentinosaurus have been found.

The scientists, meanwhile, did not reveal why the person shown in this reconstruction of the dinosaur is waving. It seems more likely they would be running, or possibly taking a selfie.

What's with the dinosaur's cool name?

The dinosaur was named Dreadnoughtus because "we thought it was time a plant-eating dinosaur got a badass name", according to researcher Matt Lamanna of the Carnegie Museum of Natural History in Pittsburgh.

"Those are usually reserved for the meat-eaters," said Mr Lamanna, a palaeontologist.

The name is drawn from the huge battleships of more than a century ago, and means "fearer of nothing".